1899] 



ENTOMOLOGICAL SOCIETY. 



85 



the cause for the sickness will soon become apparent. Small white maggots will bore 

 their way out through the skin and congregate about the poor caterpillar as in Fig 39, a; 

 and if these maggots be watched, it will be found that they soon begin to spin silken 

 cocoons about their bodies (see Fig. 39, b.) The caterpillar has sometimes sufficient 

 vitality left to crawl away from its tormentors an inch or two ; but most frequently it 

 dies beside them, and in a day or two no trace of its body can be found. If these 

 cocoons be placed in a tin box for a few days, minute four-winged flies (Fig. 39, d) will 

 emerge through a lid-like opening at the end of the cocoons. (Fig. 39, c.) These flies 

 are parasites ; they lay their eggs within the body of the cabbage- worms by inserting 

 their needle-shaped ovipositors through the skin. In a short time the eggs hatch minute 

 maggots, which grow and feed within the body of their host until they become full- 

 grown, when they emerge as already described. It is very likely that the majority of 

 cabbage worms suffer death through the agency of parasites. Even the chrysalids are 

 not immune from the attacks of these parasites ; for if many be examined, the interior of 

 the case will in some instances be found filled with small maggots. Moreover the butter- 

 fly is eaten by many birds and other animals ; so we are foreed to conclude that the 

 Cabbage fly has to contend with mauy enemies during its life-cycle (Fig. 40) ; that there 



Fig. 39.— (a) Cabbage-worm with maggots escaping through the skin ; (b) 

 The maggots have transformed into pupae within cocoons ; (c) One of the 

 cream-colored cocoons with the lid-like opening ; (d) The adult parasite fly 

 which emerges from the cocoon, greatly magnified. 



is a constant struggle for existence, and only a small fraction of the entire brood is left to 

 propagate the species and to molest the farmer and gardener. 



The respiratory or breathing apparatus of insects is rather peculiar. If a large 

 Oabbage-worm be examined many openings may be seen along each side of the abdomen 

 in the same line as the yellowish dots (Fig. 38.) These openings are the terminations of 

 tubes which ramify through the body and supply air to the interior, so that an inter- 

 change of gases can take place, and the blood be purified. 



A good practical method of killing the Oabbage-worms is to dust a mixture 

 of one pound of insect-powder and five pounds of flour through a cheese-cloth 

 bag upon the infested plants. The fine powder of the mixture clogs the breathing pores, 

 and prevents the access of air to the interior of the body, so that the worm is virtually 

 suffocated. « 



